Subject: FEL Upgrade Project Weekly Brief - December 18-22, 2006

MEMORANDUM

To: Distribution

From: F. Dylla/grn

Subject: FEL Upgrade Project Weekly Brief - December 18-22, 2006

Date: December 22, 2006

Highlights:

This is our last weekly report from the Jefferson Lab FEL team for 2006. We have used this report to list highlights of our primary accomplishments for the year in FEL physics and technology, FEL user experiments, and next generation FEL hardware development. (See below).

During FEL operations through Wednesday of this week we continued the FEL accelerator driver studies that were started last week. A detailed report on these studies by Dave Douglas has been attached to this report. Much was learned about our electron beam diagnostic systems, confidence in our electron beam transport model, and measurements on machine reproduci-

bility. During the latter part of the week, we did some upgrades on the optical transport system and replaced a faulty electrical (440v) breaker in the FEL Building. The FEL has been put in a safe shut-down until the staff returns from the holiday shut-down on Jan. 2.

On behalf of the entire FEL team and our colleagues at Jefferson Lab, we wish all of our readers a safe and enjoyable holiday season and New Year. To add to your holiday senses we have included a special shot of the FEL lasing at 1 micron with harmonic emission across the spectrum.

Key FEL Program Accomplishments in 2006
FEL Physics/Technology
High power cw lasing (14.2kW) at one of the most interesting IR wavelengths for transmission of laser light through maritime atmospheres
First demonstration of the cryo-cooled mirror concept at 40K which enabled the high power demonstration at 14 kW with no optical distortions.
Demonstration of high lasing efficiencies using a permanent magnet wiggler (>1.5% with the 20%, 1.6 micron out-coupler, and >2.3% with the 8%, 2.8 micron out-coupler). Both values are higher than our spreadsheet predictions.
First significant demonstration of the broad-band tunability of an FEL. We showed fast tuning (several seconds) over a wavelength range of 0.7-4.5 microns using a hole output-coupler.
Harmonic lasing measurement at both the third and fifth harmonic.
Demonstrated very short optical bunch lengths at 1.6 microns (down to 120 fsec).
Measurement of resistive wall heating in a narrow wiggler chamber (very important finding for scale-up designs for higher power FELs).
Design and demonstration of a clever solution for attenuating THz power before interception by the FEL optical cavity mirrors
Demonstration of a record energy acceptance of 12% for the energy
Recovery lattice when the record lasing efficiency of 2.3% was observed at 2.8 microns. (The design specification was 10%).
Development and demonstration of embedded Beam Position Monitors - an extremely low-cost, high performance system based on state-of-the art electronics
Unambiguous evidence that beams in Energy Recovered Linacs (ERLs) are manifestly non-gaussian
FEL User Results:
Very long carbon nanotube (CNT) production runs for NASA-LaRC at >1 kW on target at 1.6 microns; record production (>7 g/hr) and purity levels (> 80% single wall CNT) for laser ablation.
Delivery of 2.5 kW for a full shift for the Dahlgren NSWC laser effects experiments. Over 250 samples were exposed in two shift-long runs.
Pioneering experiments completed on differential heating of fat tissue at 1.2 and 1.7 microns; resulting in best paper for Harvard PI at International Conference of Lasers in medicine and Surgery (Boston, April 2006).
New type on THz interferometer and vacuum THz spectrometer demonstrated on THz beamline.
World’s first THZ movies
Next Generation FEL Development:
Completion of conventional construction of FEL Injector (Gun) Test Stand, and initial installation of our back-up photogun system for 500 kV tests
Receipt and start of the qualification procedures for all of the components for our joint project with AES, Inc. for fabricating a 100 mA class dc injector

Completion of the design review for our ampere class cryomodules; and mock-up of a niobium test cavity for this design
Documentation completed for a compact 100 kW demo FEL design and the associated work plan for the conceptual design phase of the project

Happy Holidays from the Jefferson Lab FEL Team:

Harmonic Light from the Jefferson Lab FEL Lasing at 1 Micron

Management:

We worked on the first complete draft of our FY06 annual report so that this documentation can be given to our review committee in January.

Gwyn Williams made a presentation of our recently obtained THz movie to DHS on Tuesday followed by attending the kick-off meeting of our Phase 3 THz project with our partner AES, Inc. at PMS-405.

WBS 3 (Beam Physics)

The attached report is a follow-on to last week’s (Dec. 15, 2006) weekly report, which cited but did not discuss, the machine operation activities intended to better our understanding of lattice and beam behavior. We have made multiple passes of detailed difference orbit measurements, correcting various minor diagnostic issues as we went. We were “presented” with an “opportunity” to study machine reproducibility as well. Given the results of these measurements, one could in principle characterize the lattice focusing well enough that meaningful emittance measurements were possible; we therefore devoted the last few days of running to various beam properties measurements. The detailed data and analysis are given in the attached report for the FEL aficionados. (The editor thanks Dave and Pavel for their concentrated efforts devoted to these important studies).

WBS 6 (RF):

The RF system was operational all week, even with some "bent" equipment for cavity 4 - 5. The 5 watt RF driver amplifier and the klystron filament board were replaced on Wednesday afternoon. This equipment will have to be tuned-up when we turn-on again in January.

Starting to investigate the M-55 equipment as to why it trips-off in normal operation, but is capable of its normal operating range under near DC conditions.

The Injector Phase Monitor system is having its GPIB communications revised. The Drive Laser pick-off isnot ready from the Optics group, butis planned for the February down. Additional thermal stabilization is likely once the entire system is installed and checked-out.

WBS 8 (Instrumentation):

A graph of FEL operational activity for the past 10 years including the key milestones and event of both the IR Demo and the 10kW upgrade has been made based on our use of the accelerator control system "Save/Restore" files. It can be viewed online at:
http://laser.jlab.org/feldoc/JlabFEL_OPS-vs-Time.pdf
Time (as usual) was spent in support of FEL operations to assist in making the FEL difference orbit measurements. The various system patch cables and cable runs being used in the FEL master oscillator, M55 phase transfer system, Happek (bunch length) system and Cathode QE scanner systems have been reviewed and documented and configuration control database ID labels have been prepared for these items. The cable labels and respective database entries will be done during the upcoming down-time.
As we prepare for upcoming changes to FEL operations due to new requirements in CyberSecurity, we have crated a unified operator account for the FEL workstations. Motivated to keep data acquisition processes running on the workstation in lieu of operator rotations, we will begin to use a generic login which is privately kept by approved FEL operators. The account is ready, but it will take time to properly migrate to using it. Other IT activities in progress this week is a Labview-based back-up program for our documentation web-server "laser.jlab.org". This program was written to target specific folders containing large files which need to be back-up in a way that doesn't fill-up the back-up disk unnecessarily fast. The back-up tool is being implemented currently. A final IT task we are setting up addition online video area monitors for the FEL using the AXIS Communications (TM) video servers.
Work continues on the Single board IOC and general purpose board. The manual for developing the application on ColdFire with RTEMS was completed this week.
Other activities for this week was designing and fabricating the Sweep Boxes for the lab rooms. We are currently assembling the boxes and preparing them for installation in the lab rooms. The stepper motor driver boxes were modified this week with added capacitors to compensate for parasitic inductance in the motors. The final stepper motor chassis is being trouble-shot; it has several channels that are shorting out the main power supply.
A new power monitor for the FEL switchgear was configured and installed. Once the network firewall issues are fixed the switchgear will have a web-based power monitoring system. The software recovery from the power outage went well. The required IOC reboots due to the outage were used to update the UHV Ion pump power supply software. The minor updates went smoothly and the channels are being archived for the Gun group. We are preparing to install a second UHV at the buncher to monitor the vacuum levels in this region during our planned increase in gun voltage.

WBS 11 (Optics):

Optics

For this final week of the year, short staffed and distractions aside, we where still able to get a considerable amount accomplished. We installed a new low power mirror cassette in User Lab 6. This will allow us to deliver FEL light to the lab once it is certified. We also took the opportunity to replace two mirror mounts in the Optical Transport System (OTS). If you remember from the last weekly, the new mounts use Belleville disk springs instead of a standard spring. Theses new mounts are significantly more robust. While the OTS was open we removed clamp around two additional mount that is believed to cause beam walking during high power beam delivery. In preparation for the OC cavity mirror work next year we pasted a 900nm OC mirror into its mount.

Advanced Drive Laser

Work on the alternative harmonic generation system continues. As part of the effort to facilitate FEL operation and study, two realtime spectrometers were installed and tested in OCR for faster data acquisition. Two documents for the annual report were completed and submitted, one on FEL optics and the other on e-beam diagnostics. We helped our ODU User’s in Lab 6 in the certification of an important laser needed during the shutdown for their experiment.

Terahertz:

This week, we performed THz transmission measurements on a sample provided by the Dept. of Homeland Security (DHS). To make these measurements required taking measurements of the beam intensity over a wide range of accelerator setups using a pyroelectric detector. From these measurements, we were able to calculate a transmission of just less than 1 %. While this may seem quite low, with a high power THz source and good detection systems, there should be sufficient signal to perform measurements through this material. We have been in discussions w/ DHS on continued work for them in the THz lab and they were pleased with the results from our first tests.
Also during the week, Gwyn was in Washington, D.C. to meet with DHS to discuss this work, as well as to meet with directors from ONR and NAVSEA for the Phase 3 Kickoff meeting for the THz research program in collaboration with Advanced Energy Systems. Both meetings went very well and we are looking forward to starting several new projects next year. While in Washington, Gwyn and Jim Kolodzey from the University of Delaware talked with several directors from the Army Night Vision Lab regarding the public release of the THz imaging tests performed in November. We have received approval for this, and we will work on publishing the results from these first tests soon.